The report revealed that about one-quarter of exclusively part-time students graduate and slightly more than half of the students who attend part-time during their college career earn a degree. However, 80 percent of exclusively full-time students attain a degree. More than 60 percent of part-time students attend community colleges, where they are the majority of the campus population.

About two-thirds of part-time students are age 24 or older, and they are more likely to support themselves financially or have children or other dependents. Three-quarters of part-time students are employed, and 42 percent of them work full-time.

"The main challenge in financing these students is the perception that Pell Grants cover the total cost of part-time students, and that's not the case," said Neal Holly, assistant director of the Postsecondary and Workforce Development Institute at Education Commission of the States. "It may cover tuition, but not fees and living expenses. That's where you need state aid to come in and fill in that gap."

But legislators are more often than not graduates of four-year institutions -- one of the most powerful lobby groups at the state level -- so institutions that have high numbers of part-time students need to do a better job of educating their local policy makers about who their students are, Holly said.

Beyond finances, institutions also have to re-evaluate how they're creating pathways for their part-time students and how they can sustain momentum and enrollment even if the student never chooses to go to full-time status.

"There is a lot out there about 15 to Finish and moving part-time to full-time, and that frankly, won't work for a lot of our part-time students," said Karen Stout, president and chief executive officer of Achieving the Dream. "Part-time isn't a deficit for our students, it's a reality, and we treat it as a deficit when it isn't."